The present invention is directed toward a method of cutting sheet material such as corrugated cardboard, and more particularly to such a method utilizing a cutting rule having a series of serrated teeth with notches therebetween for reducing the amount of paper dust from the severed cardboard.
Devices for cutting corrugated cardboard or other similar material are well known in the art. A commonly used device is the rotary die cutter. The rotary die cutter employs a cutting rule mounted on a rotating die cylinder. In operation, the cutting rule cuts through the cardboard and into a rotating anvil cylinder. The anvil cylinder is preferably covered with a resilient layer of material such as polyurethane or rubber. The teeth of the cutting rule form indentations in the anvil cover.
Many known die cutters are deficient in that a large amount of paper dust is created when the cutting rule severs the corrugated board. Paper dust creates a number of problems. For example, the paper dust ends up covering the finished product. It also interferes with printing inks that may be applied to the cardboard. In addition, the build up of the dust can lead to maintenance problems in the die cutting machine. Last but not least, the paper dust creates discomfort to workers operating the machine as it gets in their eyes and breathing passages.
Another common problem with known die cutters is that fibers from the severed corrugated board tend to become ingrained in the indentations in the anvil cover. See, for example, U.S. Pat. Nos. 3,277,764 and 3,203,295. The impregnation of fibers in the anvil cover results from the type of cutting rule that is utilized. As the serrated teeth of the cutting rule initially pass into the corrugated board, cardboard fibers located between the teeth remain. However, the wedging action of the cutting rule, as it passes through the cardboard, fractures the fibers that connect the board parts. The fibers from the severed corrugated board tend to become ingrained in the indentations in the anvil cover. The entrapped fibers eventually break apart the anvil cover. Accordingly, after a relatively short period of use the anvil cover has to be replaced. This requires the machinery to be shut off thereby creating costly downtime. Furthermore, replacement of the anvil cover itself is expensive.
Both U.S. Pat. Nos. 3,277,764 and 3,203,295 claim to minimize the build up of cardboard fibers in the anvil cover through the use of novel cutting rules. In U.S. Pat. No. 3,277,764, the cutting edge of the cutting rule comprises a plurality of equispaced sharp points separated by arcuate scallop-like cutting portions. As the cutting rule severs the workpiece, fibers located between the scallop-like cutting portions are severed by the aforementioned sharp points. Therefore, the fibers are free to become embedded in the indentations in the anvil cover. Similarly, in U.S. Pat. No. 3,203,295 the entire length of the cutting edge cuts through the workpiece. Again, this leads to the formation of a substantial amount of paper dust since no material is left between the cut pieces of corrugated board. See, also, U.S. Pat. No. 2,596,851.
Accordingly, there is a need for a method of cutting sheet material that limits the amount of paper dust created from the severed cardboard and minimizes the frequency in which the anvil cover requires replacement.